For convenience, various welding terms used in this specification are defined in the Glossary of Terms below.
Glossary of Terms
CRA: Corrosion resistant alloys. A specially formulated material used for completion components likely to present corrosion problems. Corrosion-resistant alloys may be formulated for a wide range of aggressive conditions.
HAZ: Heat-affected-zone.
Heat-affected-zone: Base metal that is adjacent to the weld line and that was affected by the heat of welding.
Toughness: Resistance to fracture initiation.
Fatigue: Resistance to fracture under cyclic loading.
Fretting fatigue: Fretting involves contact between surfaces undergoing small cyclic relative tangential motion. Fretting fatigue resistance is resistance to fracture in a notched metal parts or metal parts with holes.
Yield Strength: Ability to bear load without deformation.
FS: Friction stir.
FSW: Friction stir welding.
Friction Stir Welding: A solid state joining process for creating a welded joint between two work pieces in which the heat for joining the metal work pieces is generated by plunging a rotating pin of a tool between the work pieces.
FSP: Friction stir processing.
Friction stir processing: The method of processing and conditioning the surface of a structure by pressing a FSW tool against the surface by partially plunging a pin into the structure.
Weld joint: A welded joint including the fused or thermo-mechanically altered metal and the base metal in the “near vicinity” of, but beyond, the fused metal. The portion of the base metal that is considered within the “near vicinity” of the fused metal varies depending on factors known to those in the welding art.
Weldment: An assembly of component parts joined by welding.
Weldability: The feasibility of welding a particular metal or alloy. A number of factors affect weldability including chemistry, surface finish, heat-treating tendencies and the like.
Carbon equivalent: A parameter used to define weldability of steels and expressed by the formula CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 where all units are in weight percent.
Hydrogen cracking: Cracking that occurs in the weld subsequent to welding.
TMAZ: Thermo-mechanically affected zone.
Thermo-mechanically affected zone: Region of the joint that has experienced both temperature cycling and plastic deformation.
TMAZ-HZ: The hardest region in a weldment.
LNG: Liquefied natural gas. Gas, mainly methane, liquefied under atmospheric pressure and low temperature.
CNG: Compressed natural gas. Natural gas in high-pressure surface containers that is highly compressed (though not to the point of liquefaction).
PLNG: Pressurized liquefied natural gas. Gas, mainly methane, liquefied under moderate pressure and low temperature (higher temperature than LNG).
SCR: Steel catenary riser. A deepwater steel riser suspended in a single catenary from a platform and connected horizontally on the seabed.
TTR: Top tension riser. A riser on offshore oil rigs which is placed in tension to maintain even pressure on marine riser pipe.
Invar: An alloy of iron and nickel specifically designed to have low coefficient of thermal expansion
Duplex: Steel consisting of two phases, specifically austenite and ferrite.
Trees: The assembly of valves, pipes, and fittings used to control the flow of oil and gas from a well.
BOP: Blow Out Preventer. The equipment installed at the wellhead to control pressures in the annular space between the casing and drill pipe or tubing during drilling, completion, and work over operations.
OCTG: Oil Country Tubular Goods. A term applied to casing, tubing, plain-end casing liners, pup joints, couplings, connectors and plain-end drill pipe.
Semi-submersibles: Mobile drilling platform with floats or pontoons submerged to give stability while operating. Used in deeper waters down to 360 meters or more. Kept in position by anchors or dynamic positioning.
Jack-up rigs: Mobile drilling platform with retractable legs used in shallow waters less than 100 meters deep.
TLP: Tension Leg Platform. A floating offshore structure held in position by a number of tension-maintaining cables anchored to seabed. Cables dampen wave action to keep platform stationary.
DDCV: Deep Draft Caisson Vessel. Deep draft surface piercing cylinder type of floater, particularly well adapted to deepwater, which accommodates drilling, top tensioned risers and dry completions.
Compliant towers: Narrow, flexible towers and a piled foundation supporting a conventional deck for drilling and production operations. Designed to sustain significant lateral deflections and forces, and are typically used in water depths ranging from 1,500 to 3,000 feet (450 to 900 m).
FPSO: Floating Production Storage and Offloading vessel. A converted or custom-built ship-shaped floater, employed to process oil and gas and for temporary storage of the oil prior to transshipment.
FSO: Floating Storage and Offloading vessel. A floating storage device, usually for oil, commonly used where it is not possible or efficient to lay a pipe-line to the shore. The production platform will transfer the oil to the FSO where it will be stored until a tanker arrives and connects to the FSO to offload it.
Tendons: Tubular tethers that permanently moor a floating platform attached at each of the structure's corners.
Umbilicals: An assembly of hydraulic hoses which can also include electrical cables or optic fibers, used to control a subsea structure or ROV from a platform or a vessel.
Tender vessels: A support/supply ship for carrying passengers and supplies to and from facilities close to shore.
Strain hardening: The increase in hardness and strength of a ductile metal as it is plastically deformed.
X65: A line pipe steel with a yield strength of 65 Ksi (65,000 psi).
Electron beam welding (EBW): A welding process in which a beam of high-velocity electrons is applied to the materials being joined. The workpieces melt as the kinetic energy of the electrons is transformed into heat upon impact, and the filler metal, if used, also melts to form part of the weld. Pressure is not applied, and a shielding gas is not used, though the welding is often done in conditions of a vacuum to prevent dispersion of the electron beam.
Laser beam welding (LBW): A welding process used to join multiple pieces of metal through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates.